Wow… there are so many questions here. You really don’t hold back do you! =P.
I started studying time when I was in primary school. I also learned about planets when I was in primary school. When I was 17 I learned about black holes (secondary) and in my final year of university I was exposed to the theory behind white holes. In my last two years of university, I had a brilliant lecturer who taught me the fundamentals behind Einstein’s theory of general relativity. This is a theory which models the universe using an idea called “space time”. This space time is when you put both space and time together as one single thing. I was fascinated. It was so neat, so cool and the ideas were “intuitive”, although the maths was very difficult. For these reason I decided to pursue a PhD (an extra degree on top of the “normal” one) in this area!
To answer your question about white holes. White holes are the “time reversal” of a black hole. What this means is instead of a hole that sucks stuff in… it’s now a hole that blows stuff out. You can never enter a white hole. Einstein’s theories (his field equations) show that white holes, theoretically, must exist within our universe. However, they have never been observed and I’ll be amazed if they ever are. I hope this answers your questions!